Apparatus and method for heated food delivery

ABSTRACT

A delivery apparatus includes a container for holding an article to be delivered and a heater, and an enunciating device for displaying temperature conditions within the container. The container includes a plurality of walls forming an interior area and an opening, wherein the opening is provided with a size sufficient to allow movement of the article and the heater from outside the container to within the interior area of the container. The container includes a flap for selectively covering and uncovering the opening to allow access to the interior area of the container. The heater is constructed and arranged for placement within the interior area of the container and is provided for heating the article. The enunciating device includes a temperature sensor for sensing temperature within the container, a temperature display for displaying temperature conditions within the container, and a power source for operating the enunciating device. A method for delivering food and an enunciating device are provided.

This application is a continuation in part application of U.S. patentapplication Ser. No. 09/504,550, issued as U.S. Pat. No. 6,353,208, thatwas filed with the United States Patent and Trademark Office on Feb. 15,2000. The entire disclosure of U.S. patent application Ser. No.09/504,550 is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a delivery apparatus for keeping food productwarm during transport, and to a method for delivering food.

BACKGROUND OF THE INVENTION

Food products, such as pizza, are frequently prepared and cooked at astore location. The prepared food product is then delivered to acustomer at a home or place of business.

A freshly cooked food product may be stored at the store locationawaiting a delivery person's transportation of the food product to thecustomer. It is common to prepare pizza and store it in a cardboard box.The cardboard box is placed under a heat lamp awaiting pickup by adelivery person. The delivery person then stores the cardboard box in athermally insulated carrying case for delivery to the consumer. Despitethese methods, the product may lose heat during storage andtransportation and the temperature of the product may decrease. If theproduct becomes too cool, it may become unacceptable to a customer. As aresult, attention has been directed at techniques for keeping a foodproduct warm after it has been cooked.

The prior art describes delivery apparatus that can be used to keep fooditems warm during transportation. For example the following U.S. Patentsdescribe such prior art delivery apparatus: U.S. Pat. No. 5,999,699 toHyatt; U.S. Pat. No. 5,932,129 to Hyatt; U.S. Pat. No. 5,892,202 toBaldwin et al.; U.S. Pat. No. 5,880,435 to Bostic; U.S. Pat. No.5,884,006 to Frohlich et al.; and U.S. Pat. No. 5,750,962 to Hyatt.

SUMMARY OF THE INVENTION

A delivery apparatus is provided by the invention. The deliveryapparatus includes a container for holding an article to be deliveredand a heater, and an enunciating device for displaying temperatureconditions within the container. The container includes a plurality ofwalls forming an interior area and an opening, wherein the opening isprovided with a size sufficient to allow movement of the article and theheater from outside the container to within the interior area of thecontainer. The container includes a flap for selectively covering anduncovering the opening to allow access to the interior area of thecontainer. The heater is constructed and arranged for placement withinthe interior area of the container and is provided for heating thearticle. The enunciating device includes a temperature sensor forsensing temperature within the container, a temperature display fordisplaying temperature conditions within the container, and a powersource for operating the enunciating device.

A method for delivering food is provided by the invention. The methodincludes steps of (a) charging the delivery apparatus with thermalenergy and (b) delivering food in the delivery apparatus.

An enunciating device is provided according to the invention. Theenunciating device includes a temperature sensor for sensing temperaturewithin a container, a temperature display for displaying temperatureconditions within the container, and a power source for operating theenunciating device. The enunciating device can be constructed so that itis resistive to heat and humidity associated with food transport and isportable so that it can be attached and detached from a portabledelivery container. Preferably, the enunciating device weights less than0.5 pound and more preferably less than three ounces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustration of the delivery apparatus accordingto the principles of the present invention along with a pizza boxpartially inserted into the delivery apparatus.

FIG. 2 is a perspective view of the heater according to the principlesof the present invention.

FIG. 3 is a sectional view of the heater according to the principles ofthe present invention.

FIG. 4 is an exploded view of the assembly of the heater according tothe principles of the present invention.

FIG. 5 is a wiring diagram of the heater according to the principles ofthe present invention.

FIG. 6 is a block diagram of a controller according to the principles ofthe present invention.

FIG. 7 is a block diagram of an alternative controller according to theprinciples of the present invention.

FIG. 8 is an exemplary temperature versus time chart showing onepossible control scheme according to the principles of the presentinvention.

FIG. 9 is an exploded perspective view of a preferred embodiment of theheater of the invention.

FIG. 10 is a perspective view of a preferred embodiment of a thermostatand fuse assembly of the invention provided in FIG. 9.

FIG. 11 is a perspective view of a pizza delivery bag that includes atemperature enunciating device according to the principles of theinvention.

FIG. 12 is a sectional view of the pizza delivery bag of FIG. 11 takenalong line 12—12.

FIGS. 13(a)-(c) is a diagrammatic view of exemplary visual temperaturedisplays according to the principles of the invention.

FIG. 14 is a diagrammatic view of an exemplary audio temperature displayaccording to the principles of the invention.

FIG. 15 is a functional block diagram illustrating operation of theenunciating device according to the principles of the invention.

FIG. 16 is a functional block diagram illustrating operation of theenunciating device according to the principles of the invention.

FIG. 17 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 18 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 19 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 20 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 21 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 22 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 22A is an enlarged section of the electronic schematic diagramillustrated in FIG. 22.

FIG. 22B is an enlarged section of the electronic schematic diagramillustrated in FIG. 22.

FIG. 23 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 23A is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 23B is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 23C is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 23D is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 23E is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 23F is an enlarged section of the electronic schematic diagramillustrated in FIG. 23.

FIG. 24 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 25 is an exemplary electronic schematic diagram according to theprinciples of the invention.

FIG. 26 is an exemplary electronic schematic diagram according to theprinciples of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the various figures in which identical elementsare identically numbered throughout, a description of the preferredembodiment of the present invention will now be provided. The presentinvention will be described with reference to a delivery apparatus forfood products. In particular, the present invention will be describedwith reference to a pizza delivery bag for transporting pizzas. It iscustomary to place cooked pizza in individual cardboard boxes. While theinvention is being described in the context of a preferred embodiment,it will be appreciated that the invention can be used in a wide varietyof applications for storing and/or transporting articles where it isdesired to maintain the articles at an elevated temperature relative toambient temperature.

Now referring to FIG. 1, a container 10 having an interior area 12 isshown with a heater 14 partially inserted into the interior area 12. Thecontainer 10 can be any device having a plurality of walls forming aninterior area 12. In a preferred embodiment of the container the wallsof the container are insulated. The container 10 also includes anopening 25 constructed for movement of the article 13 in and out of theinterior area 12. The interior area 12 can be a single compartment or itcan be multiple compartments.

A preferred embodiment of the container 10 is shown in FIG. 1 as pizzabag 11. Pizza bag 11 includes bottom wall 18, top wall 16, back wall 20and first and second sidewalls 22 and 24. The walls 16, 18, 20, 22 and24 of pizza bag 11 are insulated walls.

The container 10 also includes a flap 26 for covering the opening 25.The flap 26 can be any device for covering the opening 25. The purposeof the flap 26 is to prevent heat from escaping from the interior areaof the container 10. The flap 26 could be an extension of anycombination of walls 16, 18, 20, 22 and 24. The extension of any ofthese walls would be constructed to substantially cover the opening 25.Alternatively, the flap 26 could be a separate piece that is fastened tothe container 10 to cover the opening 25. While the flap 26 does nothave to have a fastener, it is preferred. The flap 26 could be anextension of top wall 16 zippered to an extension of bottom wall 18, forexample.

In a preferred embodiment the flap 26 is an extension 27 of top wall 16.The extension 27 is draped down over the opening 25 and is slightlylonger in the vertical direction than the opening 25. The free end ofthe extension 27 wraps around to the bottom wall 18 and is attached tothe bottom wall 18 with hook and loop fastener 28. A mating hook andloop fastener is provided on the bottom wall 18.

An article 13 is shown partially received by the container 10. Thearticle 13 can be any item that needs to be heated or maintained at atemperature above ambient temperature. The article 13 could be a fooditem or it could be a non-food item. In the case of food, the article 13could be the food itself without any packaging or it could be the foodand its associated packaging. In a preferred embodiment, the article 13is a pizza box 21 including a pizza inside the pizza box 21. The article13 could also be two or more pizza boxes 21.

FIG. 2 shows the heater 14 in the absence of the bag 11. Heater 14 isany device that releases heat energy. Heater 14 can come in manydifferent configurations. A preferred embodiment of the heater 14 is a“wrap heater”. A heater can be called a wrap heater when is wraps anarticle to be kept warm. That is, it wraps or heats at least two sidesof an article to be kept warm. An exemplary wrap heater is described inU.S. application Ser. No. 09/267,182 which is assigned to VestureCorporation the assignee of the above-identified application and whichis hereby incorporated herein by reference. FIG. 2 shows a preferredembodiment of the heater 14, which is wrap heater 29.

Wrap heater 29 includes a cover 35. The cover includes anything thatcovers the heating grid and, if present, the heat sink of the heater 14.The cover can be a number of things including but not limited to a bagwith a single compartment for receiving the heating grid and heat sink.The cover can be a hard-shell container.

In a preferred embodiment, the cover 35 of the wrap heater 29 has afirst heating sleeve 30 and a second heating sleeve 32. An extension 34is provided connecting the first heating sleeve 30 to the second heatingsleeve 32. The wrap heater 29 is provided for heating a food productsuch that the first heating sleeve 30 is on one side of the food productand the second heating sleeve 32 is on the other side of the foodproduct. The first and second heating sleeves 30 and 32 and theextension 34 are preferably made of a 210 to 400 denier nylon.

Each of the first heating sleeve 30 and second heating sleeve 32 includean inside surface 15 and an outside surface 17. The inside surface 15provides a surface which is generally the closest surface of the wrapheater 29 to the article being heated. The outer surface 17 provides asurface that is closest to the bag 11 in which the wrap heater 29 isprovided. The inside surface 15 and the outer surface 17 are preferablyattached together along their edges 19 to contain the internalcomponents and to prevent foreign matter from entering into the internalcomponents of the heater 14. Preferably, the inside surface 15 and theouter surface 17 are sewn together along their edges 19. A hook and loopfastener 21 is sewn to the outer surface 17 of the receiving sleeves 30and 32. A hook and loop fastener is also sewn to the pocket side of thetop wall 16. The first hook and loop fastener 21 can be easily fastenedto the hook and loop fastener 23 on the container thereby holding thewrap heater 29 in the interior area 12 of the bag 11. An identicalsystem of hook and loop fasteners can be used to attach the outsidesurface 17 of the second receiving sleeve 32 to the pocket side of thebottom wall 16 of the bag 11.

The power cord 38 is adapted to be plugged into a power source with plug40. The power source may be an alternating current source such as a walloutlet or it may be any other power source including a direct currentpower source. The power cord 38 is attached to the wrap heater 29 via asleeve 42 that is stitched to the second heating sleeve 32. The sleeve42 is preferably of large enough diameter such that the plug 46 can bepulled through the sleeve for easy removal from the wrap heater 29. Thepower cord 38 rounds a corner of the wrap heater 29 and travels alongthe extension 34. A sleeve 44 holds the power cord 38 to the extension34. The sleeve 44 is preferably attached to the extension with afastener such as a hook and loop fastener so that cord 38 and plug 46can easily be removed from the wrap heater 29. A female plug 46 and themale plug 48 connect the cord 38 to cord 50. The purpose of the plugs 46and 48 are to allow for replacement of the cord 38 along with plugs 46and 40 without having to replace the entire wrap heater 29.Additionally, the ability to remove cord 38 with associated plugs 40 and46 allows for easy replacement with different cords and plugs that canbe used in countries with different power sources.

Cord 50 is connected to the electronics residing in a box 64 (shown inFIG. 3) that resides in sleeve 36. The wrap heater 29 includes thecontroller sleeve 36 in which a controller or a portion of a controller(not shown in FIG. 2) may be placed. Sleeve 36 is accessible from thefood product receiving area of the bag 11 via an opening that isnormally secured shut with a hook and loop fastener.

First and second light sources 52 and 54 are shown attached to thesecond heating sleeve 32. The light sources 52 and 54 are attached tothe second heating sleeve 32 via grommets (not shown).

FIG. 3 shows more detail of the wrap heater 29 of FIG. 2. In FIG. 3 thewrap heater 29 is laid open such that first heating sleeve 30, secondheating sleeve 32 and extension 34 are in the same plane. The firstheating sleeve 30 defines a pocket 56 and the second heating sleevedefines a pocket 58. In the normal operation of the wrap heater 29,assemblies 60 and 62 are located in the pockets 56 and 58 respectively.In normal operation the pockets 56 and 58 would be sewn shut with theassemblies 60 and 62 located inside the pockets 56 and 58 respectivelyso that the assemblies 60 and 62 cannot slide out. In FIG. 3 theassemblies 60 and 62 are shown outside the pockets 56 and 58 for ease ofillustration.

The first heating sleeve 30 is separated from the extension 34 by afirst crease 31. The second heating sleeve 32 is separated from theextension 34 by a second crease 33. The creases 30 and 32 allow the wrapheater 10 to generally wrap an article for heating. In the case of apizza provided in a pizza box, the first sleeve 30 can be providedcovering the top of the pizza box, and the second heating sleeve 32 canbe provided underneath the pizza box. The creases 31 and 33 also resultin a pocket 57 located in the extension 34. Pocket 57 preferablycontains a layer of polyester insulation. A layer of polyesterinsulation is also placed in the pockets 56 and 58 between therespective assemblies 60 and 62 and respective outer surfaces 17. Thisinsulation further prevents heat loss to the outside environment.

Power cord 50 that provides electrical power to the wrap heater 29 isconnected to the electronics in box 64. The box 64 is preferably analuminum box with ventilation holes. The box 64 protects and supports acircuit board contained within box 64. The circuit board contained inbox 64 includes electrical components and circuitry that make up a partof the controller. The term “controller” is not limited to theelectronics located in the box 64 but could also include othercomponents such as sensors and switches that will be described below.Furthermore, the term “controller” does not require all of the elementsin the box 64 but could comprise a smaller subset of elements.

While a brief description of the electrical connections is provided herein conjunction with FIG. 3, a more detailed discussion is set forthbelow in the discussion of FIG. 5. Two wires 70 and 72 connect the firstlight source 52 to the electronics in box 64. Likewise, two wires 74 and76 connect the second light source 54 to the electronics in the box 64.The wires 70, 72, 74, and 76 can travel along the bottom of assembly 62between the assembly 62 and the outer surface 17. Preferably the wires70, 72, 74 and 76 travel between the assembly 62 and the inside surface15. When the assemblies 60 and 62 are placed inside the pockets 56 and58, the light sources 52 and 54 can be seen through the window 51 atholes 53 and 55. The window 51 is preferably a clear flexible plasticmaterial that is sewn to the inside surface 15. The light sources arepreferably light emitting diodes (LED) with the first light source 52being a red LED and the second light source 54 being a green LED. Eachlight source 52 and 54 has at least a first state in which a first levelof light intensity is released and a second state in which a secondlevel of light intensity is released. In a preferred embodiment, thefirst state of both light sources 52 and 54 is equivalent to the LEDbeing turned on such that it releases light. In a preferred embodiment,the second state of both light sources 52 and 54 is equivalent to theLED being turned off such that no light is released.

FIG. 4 illustrates an exploded view of the elements of the assembly 62.Note that in the preferred embodiment the assembly 60 is very similar toassembly 62. Therefore, the discussion of assembly 62 below can beapplied to assembly 60.

Assembly 62 includes a heating grid 80 that is preferably a mica highwatt density heating grid. For purposes of the present invention theterm “high watt density heating grid” defines a heating grid with a wattdensity equal to or greater than 2.5 watts per square inch. In apreferred embodiment the heating grid 80 is a 300 watt mica heating gridwith an area of 100 square inches (10 inch by 10 inch square) resultingin 3.0 watts per square inch. The heating grid can be constructed ofother materials that can handle the high watt density required for thisinvention.

Assembly 62 also includes a heat sink 84 that is in thermally conductivecontact with the heating grid 80 so that a portion of the heat generatedby the heating grid 80 flows into the heat sink 84. The heat energy inthe heat sink 84 is then released for heating the article such as thepizza. The heat sink should have a phase change temperature of at least300° F. It is desired that the heat sink have a specific heat on theorder of the specific heat of polycarbonate or higher. It is also adesign consideration to have a heat sink with a relatively low density.For example, a number of metals are too dense and thus would result in avery heavy delivery apparatus if used as the heat sink. Some exemplarymaterials that might be used as a heat sink are aluminum and phnalicresins. The heat sink 84 is preferably made of polycarbonate.

The heat sink 84 can be any shape including a square, rectangle, circleor any other shape. The polycarbonate heat sink 84 is preferably in theshape shown in FIG. 4. This preferred shape of the polycarbonate heatsink 84 is essentially a square central portion 85 with four wings 87,one wing extending from each corner of the square central portion. Theadvantage of the wings 87 is that they extend over the corners of thecardboard box that holds the pizza. The corners of the cardboard box arethe strongest part of the cardboard box. Therefore, the wings 87 inconjunction with the stronger corners of the cardboard box prevent theheat sink from pressing against the central part of the box. Pressure onthe central part of the box would cause pressure into the pizza itselfincluding the cheese resulting in a less desirable food product.

The ridges 89 are depressed as compared to the rest of the polycarbonateheat sink 84 and these ridges 89 become further depressed as they slopetoward the center 91 of the polycarbonate heat sink 84. That is, thecenter 91 of the polycarbonate heat sink 84 is closer to the heatinggrid than the rest of the polycarbonate heat sink 84. This depression inthe heat sink 84 accounts for stresses caused by thermal expansion andcontraction of the heat sink 84. The depression prevents materials fromwarping and therefore restricting the space in the cover 35.

The layer 86 directs the heat energy from the heating grid 80 toward thepolycarbonate heat sink 84. The layer 86 is preferably two layers offiberglass matting, such as maniglass material, each having dimensionsthe same as the heating grid 80 such as 10 inches by 10 inches. Each ofthe two maniglass layers is preferably about one eighth of an inchthick. An advantage of using maniglass for layer 86 is that maniglass iscapable of withstanding high temperatures without emitting unpleasantodors.

The layer 88 is a structural element that holds all the elements of theassembly 62 together. Preferably the layer 88 is a sheet of aluminum.The dimensions of the layer 88 are generally the same as the squareformed by the central portion of the heat sink 84 that is 12 inches longby 12 inches wide. The layer 88 further includes four flaps 90 that arealso preferably made of aluminum. The flaps 90 extend beyond the squareshape of the layer 88 and are made to wrap around the outer edge 92 ofthe heat sink 84 so that the heat sink 84 and the layer 88 cover andhold together all the elements of the assembly 62. In FIG. 4, adhesivetape 94 is shown covering the outer edges 92 of the heat sink 84. In thefinal assembly 62, the flap 90 wraps around the outer edge 92 and thenthe tape 94 is adhesively attached to cover the flap 90 and a portion ofthe heat sink 84 as an additional means for keeping the flaps 90 frompulling apart from the heat sink 84. The tape 94 is preferably a 7 inchstrip of TYCO 225 FR tape.

A temperature sensor 100 is electrically connected to the box 64 bywires 102 and 104. The temperature sensor 100 is any device that iscapable of measuring the temperature of the heating grid such that thetemperature information can be utilized by a controller.

The temperature sensor 100 is preferably a thermister. The thermister ispreferably rated between 3 kilo ohms and 100 kilo ohms. A preferredembodiment utilizes a 10 kilo ohm thermister. In a preferred embodimentthere is no sensor in the assembly 60. A thermister 100 in the assembly62 is sufficient to provide the requisite temperature feedback forproper control of the wrap heater 29. However, there could be a sensorin the assembly 60. The thermister 100 is attached to the heating grid80 by tape 106 and 108. Fuses 112 and 114 are in series and are alsoattached to the heating grid 80 by the tape 106 and 108. The wires 102,104 and others in the assembly 62 lead out of the assembly 62 throughheat shrink tube 101 that is taped to the polycarbonate heat sink 84with tape 103. Tape 103 is preferably TYCO 225 FR tape.

It should be appreciated that while a preferred embodiment of the heaterincludes heating grids in both sleeves as shown in wrap heater 29, theheater 14 of the invention can be provided so that only one sleeveprovides heating. Furthermore, it should be appreciated that the amountof heating provided by both sleeves can vary. That is, the first sleevecan provide greater heating than the second sleeve, or vice versa.

FIG. 5 is a wiring diagram of a preferred embodiment of the invention.The heating grids 80 and 120 of assemblies 62 and 60 respectively areshown. The box 64 that contains electronics to be discussed furtherbelow is also shown.

In operation, thermister 100, thermal fuse 112 and thermal fuse 114 areattached to the heating grid 80 with tape (not shown). The thermal fuse112 is preferably a 192° C. thermal fuse. The thermal fuse 114 ispreferably a 184° C. thermal fuse. Exemplary thermal fuses 112 and 114are thermal fuses made by Thermodisk Corporation. However, other fusesmay be used including thermal fuses having different temperature setpoints and made by different manufacturers. Two fuses of slightlydifferent temperature set points are used as an extra precaution. If oneof the thermal fuses malfunctions or is defective, the other fuseprovides the necessary protection against overheating. By using fuseswith different temperature set points, it can be guaranteed that the twofuses 112 and 114 were manufactured in different batches, therebyreducing the likelihood of a defect in both.

The connectors 122, 124 and 126 connect the fuses into the circuit.Connectors 122, 124 and 126 are preferably crimp style connectors suchas Stacon crimp connectors.

In a preferred embodiment, there is no thermister on the heating grid120. However, thermal fuses 128 and 130 are connected to heating grid120 in the same fashion as the thermal fuses 112 and 114 on heating grid80. Thermal fuse 128 is preferably a 192° C. fuse and thermal fuse 130is preferably a 184° C. fuse. Each of the thermal fuses 112, 114, 128and 130 is preferably wrapped in either a polyamide film such as Kaptontape by E. I. Du Pont De Nemours and Company or fiberglass sleevingmaterial. The polyamide tape or fiberglass sleeving material is used forelectrical insulation.

From FIG. 5 it can be seen that the fuses 112 and 114 attached to theheating grid 80 are in series with the fuses 128 and 130 attached to theheating grid 120. Therefore, if any fuse is blown, power to both heatinggrids 80 and 120 is shut down.

Terminals 132, 134, 136 and 138 are connected to the box 64. Power comesin via wire 140 to terminal 136. Power flows out of the box 64 atterminal 134. Wires 142 and 144 carry power to the mica heating grids 80and 120. The blocks 146 and 148 each represent a butt splice. Neutralwires 150 and 152 exit the mica heating grids 80 and 120 respectivelyand return to terminal 132. Terminal 138 is connected to neutral wire154 that is the neutral return wire to plug 48. Wire 156 is the groundwire and is attached to the aluminum box 64 with a fork terminal 158 anda screw 160.

FIG. 6 is a block diagram of a preferred embodiment of a controller ofthe invention and its interaction with a heating grid and power source.It should be appreciated that the term “controller” as used in thisapplication could mean the combination of a number of elements and thatnot all the elements included in the controller 198 of FIG. 6 arerequired to be in a “controller”. The controller 198 in FIG. 6 is butone embodiment of the term “controller”. Note also that FIG. 7,discussed below, is an alternate embodiment of a controller inaccordance with the present invention.

The controller 198 includes a central processing unit 200 that receivespower from the power source 202. The central processing unit 200 couldbe any electronic control device capable of receiving information from asensor and determining what signals to provide to one or more otherelectronic elements to perform some task. As an example only, the otherelectronic element could be a switch that the central processing unit200 directs to turn off the electrical power from the power source 202to the heating grid 208. As a further example only, the other elementcould be an energy storage device that the central processing unit 200directs to energize a light source. A preferred embodiment of thecentral processing unit 200 is a microprocessor located on the circuitboard in the box 64.

The central processing unit is electrically connected to a switch 204.Switch 204 may be any device capable of receiving a signal from thecentral processing unit to allow or disallow energy to flow from thepower source 208 to the heating grid 208. The switch 204 must also becapable of then performing the operation of allowing or preventingenergy to flow from the power source 208 to the heating grid 208. Apreferred embodiment of switch 204 comprises solid-state electronicssuch as one or more transistors.

The temperature sensor 206 is in thermal communication with the heatinggrid 208. The temperature sensor 206 is also in electrical communicationwith the central processing unit 200. The temperature sensor is anysensor capable of communicating the temperature of the heating grid 208to another device. For example, the temperature sensor 206 communicatesthe temperature of the heating grid 208 to the central processing unit200. As stated above, in a preferred embodiment the temperature sensor206 is a thermister.

Energy storage device 210 is electrically connected to the light source212 for providing energy to the light source 212 even when the heater isnot connected to the power source 202. Energy storage device 210 is alsoin electrical communication with the central processing unit 200. Anydevice capable of storing energy and releasing that energy in the formof electricity qualifies as an energy storage device 210. In a preferredembodiment the energy storage device 210 provides energy to the lightsource 212 upon command by the central processing unit 200. The energystorage device 210 is preferably a set of capacitors provided on thecircuit board in the box 64. An alternative embodiment of the energystorage device 210 would be a rechargeable battery. The presence ofenergy storage device 210 attached to the delivery apparatus forpowering the light sources is very advantageous in that the indicatinglights can provide information even after the delivery apparatus isdisconnected from the power source.

FIG. 7 is a block diagram of an alternate embodiment of a controller ofthe present invention. The controller 241 is shown. A power source 242is connected to a relay 244. The relay 244 is any device capable ofallowing energy to flow through for a specified period of time and thenpreventing energy to flow through after that specified time has passed.The relay 244 is preferably a timer control latching relay. The relay244 allows a predetermined amount of energy to go to the heating grid246. In a preferred embodiment the timer control latching relay is setfor 2.5 minutes before the energy to the heating grid is interrupted.

The fuse 248 is for security to prevent overheating of the heating grid246. In a preferred embodiment, the fuse 248 is a 184° C. thermal fuse.

The sensor 250 is also a security component that prevents thetemperature of the heating grid from going over a particulartemperature. Sensor 250 is any device that is capable of opening thecircuit when a particular temperature is reached. In a preferredembodiment, the sensor 250 is a thermostat. In a more preferredembodiment, the sensor 250 is a normally closed thermostat that opensthe circuit at 140° C. The thermostat 250 is in thermal communicationwith the heating grid 246. If the temperature of the heating grid 246goes over 140° C. the thermostat 250 prevents further energy frompassing to the heating grid 246.

Heating grid 246 is preferably a mica heating grid but could be othertypes of heating grids as discussed above with respect to otherembodiments. In a preferred embodiment heating grid 246 is capable ofhigh watt densities of greater than 2.5 watts per square inch.

Control of the light sources 254 and 256 is shown in the rest of FIG. 7.Transformer 252 reduces the voltage from source voltage to a voltageappropriate for the light sources. In a preferred embodiment, the powersource is at 120 volts and the transformer reduces the voltage to 5volts.

The transformed down power then passes through the energy storage device258. Relay 260 is any device which can receive a signal from athermostat or other sensor and switch one or more lights on and offaccording to a particular protocol that results in providing informationto the user regarding the status of the heater. In a preferredembodiment the relay 260 is a single pole double throw thermostat drivenrelay.

The relay 260 is driven by sensor 262. Sensor 262 is in thermalcommunication with the heating grid 246. Sensor 262 is any devicecapable of determining the temperature of the heating grid 246 andcommunicating that temperature information on to the relay 260. In apreferred embodiment the sensor 262 is a normally open 66° C.thermostat. The normally open 66° C. thermostat is open when thetemperature is below 66° C. When the temperature of the heating grid 246goes above 66° C. the thermostat 262 closes the circuit.

The relay 260 drives light sources 254 and 256 according to the signalsthe relay 260 receives from the thermostat. The light sources 254 and256 are preferably a red LED and a green LED. It should be appreciatedthat it is within the scope of this invention to have only one lightsource or to have more than two light sources. The choice of how manylight sources depends on what information is desired to provide to theuser.

The operation of the device in FIG. 7 is now described. The relay 244allows power to pass through the relay 244 for a set period of time,preferably about 2.5 minutes. During the 2.5 minutes the heating grid ischarging and therefore the temperature of the heating grid 246 isrising. If the temperature goes above 140° C., the thermostat 250 opensthe circuit to prevent the heating grid 246 from receiving furtherelectrical energy. As a precaution the fuse 248 will also open thecircuit if the temperature of the heating grid rises above 184° C.

The 120 volts from the power source 242 is transformed to 5 volts bytransformer 252. The energy storage device is charged during theapproximately 2.5 minutes that the timer allows charging of the heatinggrid 246.

When the relay 244 opens the circuit after 2.5 minutes, the heating grid246 gradually cools down. The heating grid 246 will not heat up againuntil the user restarts the cycle by resetting the relay 244.

Before charging of the heating grid begins, the red and green LED's areoff. When the charging is proceeding and the temperature of the heatinggrid 246 is below the 66° C. set point of the thermostat 262, the relay260 causes the red light to be on. When the temperature of the heatinggrid exceeds 66° C., the relay 260 causes the red light to go off andthe green light to go on. When the temperature of the heating grid 246drops below 66° C., the relay 260 causes the green LED to go off and thered LED to go on. At this stage, there is no power reaching thetransformer 252 and so there is only a limited amount of energyavailable as stored in the energy storage device 258. After the energyin energy storage device 258 is expended, both light sources go off.

The control operation of the wrap heater 29 with respect to theembodiment shown in FIGS. 1-6 is now explained in conjunction with FIG.8. FIG. 8 is a graph of temperature of the heating grids 80 and 120versus time. This graph was generated from an experimental measurementof the preferred embodiment of the invention described above. The linein the graph using diamond shapes for data points is one possibletemperature curve of the heating grid 80 and the line using square datapoints is one possible temperature curve of the heating grid 120. Thegraph of FIG. 8 is not intended to be limiting to the inventiondisclosed herein. Rather the graph of FIG. 8 is merely an example of apossible control scheme. The notations along the time axis for “AC OFF”and “AC ON” represent the time at which the power to the heating gridswas turned off and on respectively.

In a preferred embodiment, the temperature of the heating grids 80 and120 cycle from an initial temperature that is room temperature to ahigher temperature and then the temperature is allowed to drop to alower temperature while the power to the heating grid is turned off.Preferably this cycle from a higher temperature to a lower temperaturewill occur three times and then the controller directed by themicroprocessor will turn the heating grids 80 and 120 off and leave themoff until a user directs the heater to begin charging again. The user sodirects the heater to begin charging again by unplugging the plug 48from the power outlet and then plugging plug 48 back into the outlet.The shut off of power to the heater after three cycles is to preventexcessive use of electricity in the case when a heater isunintentionally left on for an extended period of time. Only one cyclefrom higher temperature to lower temperature is shown in FIG. 8.

As can be seen, each cycle from AC OFF to AC ON is 30 minutes. In apreferred use of the invention the wrap heater 29 is removed from thepower source at the same time the power is turned off (AC OFF). Then theheating grids continue to heat up to approximately 240° F. Thepolycarbonate heat sink 84 then releases heat energy for an extendedperiod of time. Thirty minutes after the AC is turned off thetemperature of the heating grids is approximately 170° F. Using heatinggrids 80 and 120 with a watt density of 3.0 watts per square inch, ittakes 2.5 minutes from power on to power off to accomplish a higher orpeak temperature of 240° F. The difference between the peak temperatureand the lower temperature is referred to as the “hysteresis”. In theexample provided, the hysteresis is 240°-170°=70°.

It is noted that the use of a high watt density heating grid in theprior art devices would present significant problems. Prior art deliveryapparatus use thermostats that are not capable of providing a largehysteresis. Thermostats typically provide a hysteresis of 2-10°. With ahigh watt density heating grid of 3.0 watts per square inch, theovershoot would be much less controllable and there would certainly be ahigh risk that the thermostat would fail to perform consistently toprevent heat sink degradation. For example, in U.S. Pat. No. 5,880,435entitled “Food Delivery Container”, the replacement of the heatingelement with the high watt density heating grid of the present inventionwould result in a high risk of melt down of the polyethylene material.The thermostat of U.S. Pat. No. 5,880,435 would be in danger of failingbecause the large current flow that is required for a high watt densityheating grid would likely cause arching at the bimetallic contactpoints. Additionally, high watt density heating grid would causeunacceptable overshoot by the thermostat when the heater is powered up.

A preferred method of using the delivery apparatus in accordance withthe principles of this invention will now be described. The wrap heater29 is placed in the pizza bag 11 and attached to the pizza bag 11 asdiscussed above. If it is desirable to clean the pizza bag 11 or wrapheater 29, then the heater can be removed from the interior area 12 forcleaning. The heater is then charged with thermal energy by connectingthe heater to the power source. In a preferred embodiment, the chargingstep is accomplished by plugging the plug 48 into a wall outlet.Alternatively, the heater can be electrically connected to a battery orother power source. A further embodiment could involve a manual or othertype of switch that can be activated while the plug 48 is plugged intothe wall outlet. Activation of such a switch would result in electricalenergy flowing to the heater from the power source.

The electrical resistance heating of the heating grid then causes theheating grid to rise to a temperature of approximately 240° F. withinapproximately 2.5 minutes. A food product such as pizza or any otherfood item for which it is desirable to keep warm is placed in the foodproduct receiving area 12. The food product could be hot sandwiches,pizza, casseroles or other food items. The heater is disconnected fromthe power source. The article such as a food product is then deliveredin the delivery apparatus. The delivery step is typically carried out byplacing the delivery apparatus in a vehicle such as a car or truck anddriving the vehicle to the customers' home or business. An advantage ofthe present invention is that the delivery apparatus does not need to beplugged into a power source such as a cigarette lighter in the vehicleduring transport to the customer.

It is also noted that in accordance with the embodiment shown in FIG. 6,the pizza or other food product can be placed in the delivery apparatusafter more than 2.5 minutes from the beginning of the charging step. Forexample, a pizza bag 11 containing a wrap heater 29 may be left pluggedinto the power source for up to about 1.5 hours before the controllerallows the pizza bag 11 to cool to room temperature. Therefore anexemplary use is to leave the bag 11 and wrap heater 29 plugged into thepower source for up to about one hour and then place the pizza into thefood receiving area, unplug the heater and transport the entire deliveryapparatus to the customer. Alternatively, the food product may be placedin the delivery apparatus before the charging step. This alternativedoes not result in a cold food product because of the short amount oftime (2.5 minutes) that it takes to charge the heater.

An alternative embodiment of a heater 298 of the present invention isshown in exploded perspective view in FIG. 9. This heater 298 is placedinside a pizza delivery bag (not shown). The embodiment shown in FIG. 9utilizes a polycarbonate heat sink in conjunction with a heating gridthat is not of the high watt density category. This alternativeembodiment utilizes a thermostat to control the temperature of theheating grid.

The heating grid of FIG. 9 comprises a 4.5 ohm wound wire 300 that istaped to a polycarbonate heat sink 302. The wound wire 300 has an outputof 190 watts over a 12 inch by 12 inch heater. The resulting wattdensity is therefore approximately 1.3 watts per square inch. The woundwire 300 is attached to the polycarbonate heat sink 302 by a 9 inch by14.75 inch piece of aluminum tape 303 that covers the central portion ofthe wound wire 300. Two 12.75 inch by 2 inch strips of aluminum tape 304cover the ends of the wound wire 300 and assist in attaching the woundwire 300 to the polycarbonate heat sink 302. The male plug 306 is forconnection to a typical wall outlet. The cord 308 connects plug 306 tofemale plug 308 that receives male plug 312. Cord 308 and associatedplugs 306 and 310 may be removed from plug 312 and replaced with adifferent cord and plugs if it is desired to utilize a power source ofdifferent voltage requirements or to replace a worn cord or plug.

The power cord 314 includes ground wire 316 that is mounted to a{fraction (3/16)} inch ring tongue terminal 322 at the center of thepolycarbonate heat sink. Wire 318 is the positive power wire and itleads to a thermostat 324 and thermal fuse 326 (shown in FIG. 10). Wire320 is the returning neutral wire from the wound wire 300. Maniglasslayers 330 and 332 are situated between the wound wire 300 and theinjection molded hard-shell 334. At the other end of heater 298 is ahard-shell 336 which is constructed to mate with the hard-shell 334 toenclose the other components of the heater 298.

FIG. 10 shows the thermostat 324 and fuse 326 of the alternativeembodiment shown in FIG. 9. Wire 318 is spliced to the thermal fuse 326by a Panduit butt splice 328. The fuse 326 is in series electricalconnection with thermostat 324 that is in series connection with wire340.

When the heater 298 is assembled the hard-shell 334 is coupled tohard-shell 336 by welding. Different welding techniques may be utilizedsuch as hot plate welding and ultrasonic welding. The hard-shells 334 isconstructed of polypropylene filled with talc. The hard-shell 334 couldalso be polycarbonate or other materials with similar properties. Wire314 passes between the two hard-shells 324 and 326 at the passagecreated by indentations 342 and 344.

Now referring to FIGS. 11-12, a pizza delivery bag according to theinvention is shown at reference numeral 400. The pizza delivery bagincludes an enunciating device 402. The enunciating device is anarrangement that provides a user or customer with desired informationabout the temperature conditions within the bag. The pizza delivery bagis a type of delivery apparatus according to the invention that can beused to transport and deliver various items or articles to be kept warm.Preferred items or articles to be kept warm include food such as pizza.Furthermore, the enunciating device can be used to display temperatureor thermal conditions within the delivery apparatus and, if desired,provide control of the temperature or thermal conditions within thedelivery apparatus. The delivery apparatus which includes an enunciatingdevice can be referred to as a “smart bag” because of the informationaldisplay properties, and, if desired, the control properties exhibited bythe apparatus.

The enunciating device allows a customer to have confidence that thefood arriving in the delivery container is arriving at a desired thermalcondition. In addition, the enunciating device provides an additionalquality control measure to insure that the food product is delivered ata specified temperature. Accordingly, the enunciating device can be usedto provide desired information about the thermal condition ortemperature of the article provided within the container.

The enunciating device can be a visual enunciating device or an audioenunciating device. The enunciating device 402 is shown as a visualenunciating device 404. The visual enunciating device 404 is shownhaving a plurality of lights 406 and 408 that can function similar tolight sources 254 and 256. Illumination of light 406 can indicate thatthe bag 400 is charging, and illumination of light 408 can indicate thatthe temperature in the bag is at least about 140° F. In general, itshould be understood that the temperature of a heating element or a heatsink in the bag is preferably measured rather than the actual ambienttemperature in the bag. The ambient temperature in the bag can becalculated based upon the measured temperature of the heating element orthe heat sink. As the bag 400 is used and an article is either movedinto the bag or removed from the bag, it is expected that the ambienttemperature in the bag will change but will return to a desiredtemperature that is above about 140° F. The Food and Drug Administrationhas specified that 140° F. is a hot hold food safe temperature fortransporting food.

The lights 406 and 408 can be provided as red and green lights, forexample. It is expected that a start-up protocol can include a solid redlight changing to flashing red indicating that the bag 400 is charging.The red light switch is off and the green light switch is on when thereadiness set point threshold has been achieved. The readiness set pointthreshold refers to the temperature of the heating element or the heatsink provided within the bag 400. Preferably, the readiness set pointthreshold is at least about 200° F. It is believed that the readinessset point threshold can be used to fairly accurately calculate thetemperature within the bag 400 in which the article to be heated 410 isexposed. Preferably, the article 410 includes a food item such as apizza 412 provided within a cardboard box 414.

The bag 400 includes a top wall 416, a bottom wall 418, a rear wall 420,and side walls 422 and 424. Preferably, the walls include an insulationmaterial 426 for reducing heat transfer from the interior area 428 ofthe bag 400 to exterior of the bag. The amount of insulation 426provided in the walls can vary. As shown in FIG. 12, the top wall 416includes a greater thickness of insulation material 426 than the bottomwall 418.

The bag 400 includes an interior area 428 that includes the article tobe heated 410 and the heater 430. In general, the interior area 428refers to the area within the bag 400 provided between the interiorsurfaces 432 of each wall. The interior area 428 includes an articletransport area 440 and a heater storage area 442. The heater 430 can becontained within the heater storage area 442 by a holder 444.Preferably, the holder 444 includes a fabric cover 446 for containingthe heater 430 in place. Preferably, the article 410 can be providedresting on the heater 430 and in thermally conductive contact with theheater 430. It should be appreciated that the phrase “thermallyconductive contact” refers to the existence of heat transfer from theheater to the article. There is no requirement of direct contact betweenthe heater and the article, although direct contact can be preferred.Preferably, the holder 444 includes a window 445 that allows viewing ofthe enunciating device 402.

The bag 400 includes a flap 450 that covers the bag opening. The flap450 is selectively movable between an open position and a closedposition. As shown in FIGS. 11 and 12, the flap 450 is provided in aclosed position. When the flap 450 is moved to an open position, thearticle 410 can be removed from the bag 400.

The flap 450 can include a transparent material 452. By manufacturing atleast a portion of the flap as a transparent material 452, it ispossible to provide a window 453 for visually observing the enunciatingdevice 402 provided within the interior area 428. The flap can beprovided as an opaque material such as a fabric. In the case of an audioenunciating device, it is believed that it is not necessary to provide awindow for viewing the interior of the bag. Furthermore, the flap 450can be provided as a non-transparent material (to visible light) whenthe enunciating device is provided so that it is visible when the flap450 is provided in the closed position, or when it is decided to besufficient to only view the enunciating device when the flap 450 isprovided in an open position. For example, the enunciating device can beprovided attached to the bag exterior 455 or can be provided so that ithangs outside of the bag exterior 455. The flap can be held in a closedposition by a fastener 454 such as a hook and loop fastener system 456.

The bag 400 can include handles 460 and 462 for transporting the bag.The heater 430 can be heated by electrical energy. A power cord 464 canbe provided for providing electrical connectivity between the heater 430and a power source. The power source can be provided by alternatingcurrent or direct current. The power cord 464 includes a plug 466 forconnecting to a desired power source.

The heater can include a heating element 433 such as a resistive heatingelement, an induction heating element, and/or a microwave heatingelement. The heater can include a heat sink 435. The heat sink can be asensible and/or latent polymeric based material, a sensible and/orlatent ceramic-based material, a sensible and/or latent metal enclosure,and/or a latent heat storage micro encapsulated material. A preferredmicro encapsulated material is in the form of a foam or gel and isavailable from Frisbee Technology. The heating element and heat sinkmaterial can be any of those materials previously referred to in thispatent application. The power source for powering the enunciating devicecan include a conventional 120 and/or 220 volt line voltage input, avoltage reducing a current source transformer driven electronicisolating circuit, a conventional electronic non-isolated circuit, abridge rectifier, a battery, a charged capacitor such as a standardbattery and a rechargeable battery, and an induction driven, bagmounted, secondary coil (24 volts) with input/output enunciation devicepower supply only or with control and resistive grid power supply (24volt).

The bag 400 includes a control unit 436 provided within a container 439.The control unit 437 includes a power connection 441 for instructing theheater 430 to heat. Additionally included is a temperature sensor 443for sensing the temperature of the heating element 433 and/or the heatsink 435. The control unit 437 controls the supply of power receivedthrough the power cord 464. In addition, the enunciating device 402 canbe connected to the control unit 437 or it can include its own controlunit and its own sensor and power supply.

Now referring to FIGS. 13 and 14, enunciating devices are shown. FIGS.13(a)-(c) shows visual enunciating devices 500. FIG. 13(a) shows arounded visual enunciation device 504. FIG. 13(b) shows a rectangularvisual enunciation device 505. The rectangular visual enunciation device505 is preferably in the form of lighted pipes 506. FIG. 13(c) shows anumeric visual enunciation device 508. The numeric visual enunciationdevice 508 includes three characters 510. Preferably, the visualenunciation devices are provided as LED displays.

An alternative enunciating device according to the invention can bereferred to as an audio enunciating device. As shown in FIG. 14, anaudio enunciating device 512 is shown. The audio enunciating device 512preferably includes a voice chip 514 that synthesizes a human voice foraudibly indicating the temperature within the delivery bag once providedwith stimulation. It is believed that the voice chip can be stimulatedby pressing a button and/or by opening the delivery bag.

Now referring to FIGS. 15 and 16, functional block diagrams foroperating the enunciation device according to the invention areprovided. FIG. 15 shows a functional block diagram that does not includea control for controlling the temperature within the delivery bag. Thefunctional block diagram 520 includes a power source 522, a trigger 524,a temperature sensor 526, and a display 528. In general, the powersource 522 can include any power source sufficient to drive the circuit523. Preferred power sources include batteries including commerciallyavailable batteries and rechargeable batteries. In addition, the powersource can be induction driven. That is, when the heating source for thedelivery bag is driven by induction heating, a secondary coil can beprovided which charges upon exposure to the induction force, therebyproviding a power source for operating the circuit 523. In addition, thepower source can be bridge rectified, voltage reduced current source,charged capacitor, and/or transformer driven isolated circuit. Thetrigger 524 can be any trigger that generates the display 528. It ispossible that the trigger 524 is always on thereby always causing thedisplay 528 to enunciate the temperature conditions within the deliverybag. Of course, the enunciating device can be provided without a triggerso that it is always “on.” In order to prolong the longevity of thepower source 522, it is possible to provide a trigger 524 which, whenactivated, causes the display 528 to enunciate the temperatureconditions within the delivery bag. The trigger can be a button, aswitch, and any opto coupler switch such as a light sensor or photocellor an infrared emitter/receiver switch. The temperature sensor 526 canbe any temperature sensor such as a thermometer or thermocouple thatsenses the temperature conditions within the delivery bag. Thetemperature sensor can include a thermister, a thermocouple, an RTD,and/or bimetal thermostat. The display 528 is preferably an enunciatingdevice such as one of the enunciating devices previously described.Preferred displays include digital readouts, alternating light patternsdemonstrating different conditions, and voice chips.

FIG. 16 shows a functional block diagram 540 including a power source542, a trigger 544, a temperature sensor 546, a control 548, and adisplay 550. It should be appreciated that the power source 542, thetrigger 544, the temperature sensor 546, and the display 550 can besimilar to the power source 522, the trigger 524, the temperature sensor526, and the display 528. The diagram 540 is different from the diagram520 in that the diagram 540 includes a controller 548. The controller548 is preferably provided for controlling the temperature within thedelivery bag. Accordingly, the controller 548 is preferably providedwith an ability to generate a feedback to the heating element within thedelivery bag.

The enunciating device is preferably constructed to work when connectedto a secondary power source and continue working when disconnected fromthe secondary power source. That is, it can be powered by its primarypower source. In addition, the enunciating device is preferably portablewhich means that it can be attached and detached from a deliveryapparatus. Furthermore, the enunciating device is preferably constructedto be operated at a temperature greater than 140° F., and issufficiently light weight. Preferably, the enunciating device weighsless than 0.5 lb. and preferably less than three ounces. In addition,the enunciating device preferably can be either permanently installed ina delivery apparatus or retrofitted to a variety of delivery apparatusand to the heat sink of the delivery apparatus.

The above specification, examples and data provide a completedescription of the manufacture and use device of the invention. Sincemany embodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

We claim:
 1. A pizza delivery apparatus comprising: (a) a containercomprising a plurality of walls defining a container interior; (i) saidcontainer including an opening sized for movement of at least one pizzabox into and out of the container interior; (ii) said containerincluding a flap positioned for selective closing of the opening; (b) anenunciating device comprising: (i) a temperature sensor for sensing atemperature condition within the container; (ii) an electrically powereddisplay for displaying information concerning a temperature conditiondetected by the temperature sensor; and (iii) an enunciating devicepower source for electrically powering the electrically powered display;(c) a heater selectively positionable within the container in heattransfer relationship with the container interior; said heater beingpowered by a heater power source; and, (d) a heater controllercomprising: (i) a switch electrically coupled to the heater foractivating and deactivating power from a heater power source to theheater; and, (ii) a central processor unit configured to control theswitch to: (A) cause heating of the heating grid from an initialtemperature to a higher temperature, said higher temperature being atleast 240° F.; (B) allow the heating grid to cool to a lowertemperature; and, (C) thereafter operate the control switch, asprogrammed, in response to detected temperature conditions; (D) saidhigher temperature being at least 30° F. higher than said lowertemperature.
 2. A pizza delivery apparatus according to claim 1 wherein:(a) said heater comprises a heating grid having a watt density of atleast 2.5 watts per square inch.
 3. A pizza delivery apparatus accordingto claim 2 wherein: (a) the heating grid is a mica heating grid.
 4. Apizza delivery device according to claim 3 wherein: (a) the heating gridis a 300 watt mica heating grid.
 5. A pizza delivery device according toclaim 3 wherein: (a) the heater includes a polycarbonate heat sink.
 6. Apizza delivery device according to claim 5 wherein; (a) saidpolycarbonate heat sink is positioned such that, when said pizzadelivery device is used to deliver pizza, at least a portion of saidpolycarbonate heat sink is positioned between said mica heating grid andsaid pizza.
 7. A pizza delivery device according to claim 5 wherein: (a)the polycarbonate heat sink has a shape comprising a square centralportion with four wings, one wing extending from each corner of thesquare central portion.
 8. A pizza delivery device according to claim 7wherein: (a) the heating grid has an area of 100 square inches.
 9. Apizza delivery apparatus according to claim 2 wherein: (a) the heatinggrid has a watt density of at least 3.0 watts per square inch.
 10. Apizza delivery apparatus according to claim 2 wherein: (a) the heater isof a type to be powered by an AC power source and includes an AC powercord.
 11. A pizza delivery apparatus according to claim 10 wherein: (a)the enunciating device power source comprises a capacitor arrangementpositioned to selectively power the electronically powered display ofthe enunciating device when the heater is not connected to an AC powersource.
 12. A pizza delivery apparatus according to claim 11 wherein:(a) the electrically powered display of the enunciating device includesat least one LED.
 13. A pizza delivery apparatus according to claim 12wherein: (a) the electrically powered display of the enunciating deviceincludes a green LED.
 14. A pizza delivery apparatus according to claim1 wherein: (a) said container includes: a bottom wall, a top wall, aback wall, and first and second sidewalls.
 15. A pizza deliveryapparatus according to claim 14 wherein: (a) said flap comprises anextension of at least one of the bottom wall, top wall, first sidewalland second sidewall.
 16. A pizza delivery apparatus according to claim15 wherein: (a) the container includes a hook and loop fastenerpositioned to selectively secure the flap in a closed orientation.
 17. Apizza delivery apparatus according to claim 16 wherein: (a) thecontainer includes handles for transporting the bag.
 18. A pizzadelivery device according to claim 1 wherein: (a) the enunciating devicepower source comprises a rechargeable battery arrangement positioned toselectively power the electronically powered display of the enunciatingdevice when the heater is not connected to a power source.